How does one change the tuning standard in Dorico mid-piece? Is it possible? I’m doing microtonal fluid stuff all the time, and so far I’ve worked around this limitation, but the stuff I’m doing now is too intense to neglect knowing about this any longer. Specifically, I’m looking to have A4 = 440 in a few earlier bars, and then change to A4 = 447 directly on another bar. (In the YouTube video “America the Beautiful in EVERY TET from 1 to 24”, I simply denote the tuning changes with text, but didn’t actually figure out how to change the tuning standard MID-PIECE in Dorico itself - in this new project I’m working on, I need the software itself to reflect it as part of an extremely intense transcription). I already know that I can change tuning standard globally in the playback options, and that having other programs open (messing with sample rate) can affect it. Please help!!! 
Not possible, unfortunately. The pitch setting applies to the whole file.
Questions:
- Does this setting change the overall tuning of the Halion VST?
- I don’t suppose we can override this via sysex in Dorico?
No, the tuning value in Playback Options affects the tuning of each note as it is sent to the VST instrument, rather than manipulating some global setting or other.
It would in theory be possible for us to create a “tuning change” object that could change that value at a particular point in the flow, but no such thing currently exists and I can’t imagine that it would have sufficiently wide benefit to be worth our while implementing any time soon, I’m afraid.
Well, I’ll do anything I can to help get that implemented. If it helps, I think there are a lot more casual microtonalists, mostly using 12-TET adjacent tunings, that would REALLY find it useful (like in June Lee’s transcription of Jacob Collier’s Christmas song or Chris Bandy’s work)